Effects of high magnesium intake on bone mineral status and lipid metabolism in rats

Cardiovascular safety of calcium, magnesium and strontium: what does the evidence say?

Calcium, magnesium and strontium have all been implicated in both musculoskeletal and cardiovascular health and disease. However, despite these three elements being closely chemically related, there is marked heterogeneity of their characteristics in relation to cardiovascular outcomes. In this narrative review, we describe the relevant evidential landscape, focusing on clinical trials where possible and incorporating findings from observational and causal analyses, to discern the relative roles of these elements in musculoskeletal and cardiovascular health. We conclude that calcium supplementation (for bone health) is most appropriately used in combination with vitamin D supplementation and targeted to those who are deficient in these nutrients, or in combination with antiosteoporosis medications. Whilst calcium supplementation is associated with gastrointestinal side effects and a small increased risk of renal stones, purported links with cardiovascular outcomes remain unconvincing. In normal physiology, no mechanism for an association has been elucidated and other considerations such as dose response and temporal relationships do not support a causal relationship. There is little evidence to support routine magnesium supplementation for musculoskeletal outcomes; greater dietary intake and serum concentrations appear protective against cardiovascular events. Strontium ranelate, which is now available again as a generic medication, has clear anti-fracture efficacy but is associated with an increased risk of thromboembolic disease. Whilst a signal for increased risk of myocardial infarction has been detected in some studies, this is not supported by wider analyses. Strontium ranelate, under its current licence, thus provides a useful therapeutic option for severe osteoporosis in those who do not have cardiovascular risk factors.

Microwave processing of calcium phosphate and magnesium phosphate based orthopedic bioceramics: A state-of-the-art review

The main theme of this paper is to review microwave-assisted synthesis and processing of calcium and magnesium phosphate bioceramics. Microwave processing of advanced materials has been an active field of research for the last three decades and has been already reviewed in the literature. Microwave processing of bioceramics is being pursued for almost the same period of time. Unfortunately, to the best of our knowledge, we are not aware of any comprehensive review in the literature. Our group has been a significant contributor to the field, and we feel that it is an appropriate time for reviewing the state-of-the-art of the field. The paper is divided into several sections. After rationalizing the motivation behind writing this paper in the introduction, the second section builds on some fundamental aspects of microwave-matter interactions. The third section, representing the synthesis aspects, is subdivided into five sub-sections focusing on various calcium and magnesium phosphates in both crystalline and amorphous forms. The fourth section focuses on magnesium phosphate-based bioceramics. The fifth and the sixth section describe results on the utility of microwave assistance in developing multi-functional coatings on medical implants and orthopedic cements respectively. The subsequent section reviews results on microwave sintering of calcium and magnesium phosphates. The paper concludes with remarks on unresolved issues and future directions of research. It is expected that this comprehensive review on the interdisciplinary topic will further propel the exploration of other novel applications of microwave technology in processing biomaterials by a diverse group of scientists and engineers. STATEMENT OF SIGNIFICANCE: 1. This review highlights the broad-spectrum capabilities of microwave applications in processing orthopedic bioceramics. 2. The article covers "processing" in the broadest sense of the word, comprising of material synthesis, sintering, coating formation, and setting of orthopedic cements. It also expands beyond conventional calcium phosphates to include the emergent family of magnesium phosphates. 3. In vitro/in vivo responses of microwave-processed bioceramics are discussed thus providing an integral understanding of biological aspects of these materials. 4. The comprehensive review on this interdisciplinary topic will help researchers in various disciplines to appreciate the significance and usefulness of microwaves in biomaterials processing. Further, we also believe that it will propel the exploration of other novel applications of microwave technology in the biomaterials sector.

The effect of dietary magnesium and caseinphosphopeptides on bone metabolism in rats

The effect of dietary magnesium (Mg) or caseinphosphopeptides (CPPs) on bone metabolism has been reported. However, few studies have investigated the effects of simultaneous supplementation of Mg and CPPs. Sixty-three 3-week-old Sprague-Dawley male rats were divided into seven groups and fed a specified diet for 45 days. Body characteristics, bone physicochemical indicators, and bone metabolism indicators relative to bone metabolism were analyzed. We found that, first, a dietary Mg deficiency resulted in increased bone formation and decreased bone resorption. Second, dietary Mg or CPP supplementation promoted bone formation and prevented bone resorption. Third, dietary Mg supplementation with CPPs also functioned to enhance bone formation and prevent bone resorption. There were synergistic effects on femur length, serum parathyroid hormone level and urinary deoxypyridinoline of the HS-Mg-CPP group (0.2% Mg, 0.1% CPPs). The increase in the femur length of the HS-Mg-CPP group compared with the control group was 6% which was much higher than that of HS-Mg (1%) or CPPs (5%). The induction in serum parathyroid hormone content in the HS-Mg-CPP group was 33% compared with the control group which was higher than that of the induction of the HS-Mg (19%) or CPP (23%) group. The induction in the deoxypyridinoline content of the HS-Mg-CPP (43%) group compared with the control group was remarkably higher than that of HS-Mg (8%) or CPPs (16%). Overall our results demonstrated that high doses of Mg (0.2%) and CPPs (0.1%) in combination produced synergistic effects on femur length, serum parathyroid hormone level and urinary deoxypyridinoline in rats, which is important for a better understanding of the effect of Mg and CPPs on bone metabolism.

A feasibility study of using biodegradable magnesium alloy in glaucoma drainage device

Technological advances in glaucoma have challenged the traditional treatment paradigm. Historically incisional surgery has been used in cases of advanced disease and/or uncontrolled intraocular pressures resistant to medical or laser interventions. More recently, perhaps due to advancements in imaging, surgery has been suggested to be beneficial earlier in the treatment paradigm. Despite these trends, surgical manipulation of the tissues and unpredictability of wound healing continue to result in surgical failure. Magnesium is an essential element for human body and plays a critically important role in maintaining the functional and structural integrity of several tissues, including the eye. Due to several of its advantageous properties such as non-toxicity, biodegradability, and high biological compatibility, magnesium alloy has attracted great attention as a novel biomaterial. Biodegradable cardiovascular stents made of magnesium alloy have already been introduced into clinical practice. The purpose of this review is to determine if bioabsorbable magnesium alloys can be utilized as a promising candidate for the development of a new generation of glaucoma surgical assistive devices.

Bone Mineral Density, Mechanical, Microstructural Properties and Mineral Content of the Femur in Growing Rats Fed with Cactus Opuntia ficus indica (L.) Mill. (Cactaceae) Cladodes as Calcium Source in Diet

Mechanical, microstructural properties, mineral content and bone mineral density (BMD) of the femur were evaluated in growing rats fed with Opuntia ficus indica (L.) Mill. (Cactaceae) cladodes at different maturity stages as calcium source. Male weanling rats were fed with cladodes at early maturity stage (25 and 60 days of age, belonging to groups N-60 and N-200, respectively) and cladodes at late maturity stage (100 and 135 days of age, belonging to groups N-400 and N-600, respectively) for 6 weeks. Additionally, a control group fed with calcium carbonate as calcium source was included for comparative purposes. All diets were fitted to the same calcium content (5 g/kg diet). The failure load of femurs was significantly lower (p ≤ 0.05) in groups N-60 and N-200 in comparison to N-400, N-600 and control groups. The cortical width (Ct.Wi) and trabecular thickness (Tb.Th) of the femurs in control and N-600 groups were significantly higher (p ≤ 0.05) than Ct.Wi and Tb.Th of femurs in groups N-60 and N-200. Trabecular separation of the femurs in N-60 and N-200 groups showed the highest values compared with all experimental groups. The highest calcium content in the femurs were observed in control, N-600 and N-400 groups; whereas the lowest phosphorus content in the bones were detected in N-200, N-600 and N-400 groups. Finally, the BMD in all experimental groups increased with age; nevertheless, the highest values were observed in N-600 and control groups during pubertal and adolescence stages. The results derived from this research demonstrate, for the first time, that the calcium found in Opuntia ficus indica cladodes is actually bioavailable and capable of improving mineral density and mechanical and microstructural properties of the bones. These findings suggest that the consumption of cladodes at late maturity stage within the diet might have a beneficial impact on bone health.

Magnesium intake, bone mineral density, and fractures: results from the Women's Health Initiative Observational Study

BACKGROUND

Magnesium is a necessary component of bone, but its relation to osteoporotic fractures is unclear.

OBJECTIVE

We examined magnesium intake as a risk factor for osteoporotic fractures and altered bone mineral density (BMD).

DESIGN

This prospective cohort study included 73,684 postmenopausal women enrolled in the Women's Health Initiative Observational Study. Total daily magnesium intake was estimated from baseline food-frequency questionnaires plus supplements. Hip fractures were confirmed by a medical record review; other fractures were identified by self-report. A baseline BMD analysis was performed in 4778 participants.

RESULTS

Baseline hip BMD was 3% higher (P < 0.001), and whole-body BMD was 2% higher (P < 0.001), in women who consumed >422.5 compared with <206.5 mg Mg/d. However, the incidence and RR of hip and total fractures did not differ across quintiles of magnesium. In contrast, risk of lower-arm or wrist fractures increased with higher magnesium intake [multivariate-adjusted HRs of 1.15 (95% CI: 1.01, 1.32) and 1.23 (95% CI: 1.07, 1.42) for quintiles 4 and 5, respectively, compared with quintile 1; P-trend = 0.002]. In addition, women with the highest magnesium intakes were more physically active and at increased risk of falls [HR for quintile 4: 1.11 (95% CI: 1.06, 1.16); HR for quintile 5: 1.15 (95% CI: 1.10, 1.20); P-trend < 0.001].

CONCLUSIONS

Lower magnesium intake is associated with lower BMD of the hip and whole body, but this result does not translate into increased risk of fractures. A magnesium consumption slightly greater than the Recommended Dietary Allowance is associated with increased lower-arm and wrist fractures that are possibly related to more physical activity and falls.

Effect of magnesium deficiency on various mineral concentrations in rat liver

Magnesium (Mg) deficiency is well known to affect metabolism of some trace minerals. We investigated the effect of Mg deficiency on hepatic concentration of various minerals in rats. Twelve 5-week-old male rats were divided into the groups given a control diet and an Mg-deficient diet. After 4 weeks, liver sample was collected from each rat. The concentrations of 36 minerals were simultaneously determined by a semiquantitative method of inductively coupled plasma-mass spectrometry (ICP-MS). The semiquantitative analysis showed that Mg deficiency significantly increased iron (Fe), copper (Cu), zinc (Zn), gallium (Ga), yttrium (Y), zirconium (Zr), molybdenum (Mo), rhodium (Rh), silver (Ag), and barium (Ba) concentrations, and significantly decreased scandium (Sc) and niobium (Nb) concentrations in rat liver. Then, hepatic Fe, Cu, Zn, Sc, Zr, and Mo concentrations were quantitatively measured, which indicated the similar effects as observed by the semiquantitative analysis. Additionally, the semiquantitative measurements of these minerals were highly correlated to these measurements with the quantitative method, but the measurements were not completely consistent between these analyses. The present study is the first research indicating the changes of hepatic Ga, Y, Zr, Mo, Rh, Ag, Ba, Sc, and Nb concentrations in Mg-deficient rats. The present study also indicates that the semiquantitative analysis with ICP-MS is a valid method for screening analysis to investigate various mineral concentrations in animal tissues.

Influence of therapy with metformin on the concentration of certain divalent cations in patients with non-insulin-dependent diabetes mellitus

Research was performed on a group of 30 patients with non-insulin-dependent diabetes mellitus (NIDDM), who never received antidiabetic medication before, and on a group of 17 healthy adults. The patients were administered treatment with metformin, 1,000 mg/day. Plasmatic and urinary concentration of magnesium have been measured, copper and zinc along with the concentrations of glucose, HDL, LDL, cholesterol, tryglicerides, HbA1c, and total erythrocyte magnesium, in advance and after 3 months of treatment. Data showed significant differences in the NIDDM group vs the control group: for plasma magnesium-1.95 ± 0.19 vs 2.20 ± 0.18 mg/dl, p < 0.001; urine magnesium-237.28 ± 34.51 vs 126.25 ± 38.22 mg/24 h, p < 0.001; erythrocyte magnesium-5.09 ± 0.63 vs 6.38 ± 0.75 mg/dl, p < 0.001; plasma zinc-67.56 ± 6.21 vs 98.41 ± 20.47 μg/dl, p < 0.001; urine zinc-1,347.54 ± 158.24 vs 851.65 ± 209.75 μg/24 h, p < 0.001; plasma copper-111.91 ± 20.98 vs 96.33 ± 8.56 μg/dl, p < 0.001; and urine copper-51.70 ± 23.79 vs 36.00 ± 11.70 μg/24 h, p < 0.05. Treatment with metformin for 3 months modified significant erythrocyte magnesium-5.75 ± 0.61 vs 5.09 ± 0.63 mg/dl, p < 0.001 and urine magnesium-198.27 ± 27.07 vs 237.28 ± 34.51 mg/24 h, p < 0.001, whereas it did not modify significant the plasmatic and urinary concentration of the other cations. The erythrocyte magnesium concentration was inversely correlated with HbA1c (r = -0.438, p = 0.015). The plasma level of copper was positively correlated with HbA1c (r = 0.517, p < 0.003), tryglicerides (r = 0.534, p < 0.003), and cholesterol (r = 0.440, p < 0.05), and the plasma level of zinc was inversely correlated with glycemia (r = -0.399, p = 0.029). Our data show a significant action of metformin therapy, by increasing the total intraerythrocyte magnesium concentration and decreasing the urinary magnesium elimination, positively correlated with the decrease of glycemia and HbA1c in NIDDM patients.

Fabrication of novel PLA/CDHA bionanocomposite fibers for tissue engineering applications via electrospinning

The main theme here is to fabricate PLA (poly lactic-acid)/CDHA (carbonated calcium deficient hydroxyapatite) bionanocomposites, where both the constituents are biocompatible and biodegradable with one dimension in nanometer scale. Such materials are important in tissue engineering applications. The bionanocomposite fibers were fabricated via electrospinning. There are two important signatures of this paper. First, CDHA, rather than HA, is added to PLA as the second phase. As opposed to HA, CDHA mimics the bone mineral composition better and is biodegradable. Therefore, PLA/CDHA fibers should have better biodegradability while maintaining a physiological pH during degradation. To the best of our knowledge, this is the first attempt of electrospinning of such a composite. Second, the CDHA nanoparticles were synthesized using the benign low temperature biomimetic technique, the only route available for the retention of carbonate ions in the HA lattice. The structural properties, degradation behavior, bioactivity, cell adhesion, and growth capability of as-fabricated PLA/CDHA bionanocomposites were investigated. The results show that the incorporation of CDHA decreased PLA fiber diameters, accelerated PLA degradation, buffered pH decrease caused by PLA degradation, improved the bioactivity and biocompatibility of the scaffold. These results prove that PLA/CDHA bionanocomposites have the potential in tissue regeneration applications.

Low cardiovascular risks in the middle aged males and females excreting greater 24-hour urinary taurine and magnesium in 41 WHO-CARDIAC study populations in the world

Background

Since taurine (T) administration was proven to decrease blood pressure (BP) and stroke mortality in stroke-prone spontaneously hypertension rates (SHRSP) in the 1980’s and our WHO-coordinated CARDIAC (Cardiovascular Diseases and Alimentary Comparison) Study demonstrated that among 5 diet-related factors, namely total cholesterol (T-Cho), body mass index (BMI), sodium (Na), magnesium (M), and T to creatinine (Cr) ratio in 24-hour urine (24U), both T/Cr and M/Cr were inversely related to coronary heart disease mortalities in males and females and T/Cr was inversely related to stroke mortalities in males and females. We further analyzed the associations of individual T/Cr and M/Cr levels to cardiovascular risks in the present study.

Method

From WHO-CARDIAC Study populations, 61 populations of 25 countries in the world, Japanese populations with obviously higher 24U T excretion because of their common fish eating custom and the other populations in which both data of T and M were not available were excluded and the data of 3960 individuals from 41 WHO-CARDIAC Study populations were used for the following analyses.

Results

The means of 24U T/Cr and M/Cr ratios in total individual data were 639.4 and 82.8, respectively. The average of BMI, systolic and diastolic blood pressure (SBP, DBP), T-Cho and atherogenic index (AI) in the individuals with more than the means of T/Cr or M/Cr were significantly lower than those of individuals with less than the means. The CARDIAC Study participants were divided into the following 4 groups by these means: A (T/Cr and M/Cr ≧ mean), B (T/Cr ≧ mean, M/Cr < mean), C (T/Cr < mean, M/Cr ≧ mean), D (T/Cr and M/Cr < mean). The group A showed significantly lower values compared with the group D in BMI, SBP, DBP, T-Cho, and AI.

Conclusions

Cardiovascular risks were proven to be highly significantly lower in individuals who were excreting both 24U T and M, more than the averages despite differences in ethnicity and genetic background. Since T and M are biomarkers for seafood, vegetables, soy, nuts, milk, etc., dietary custom to eat these food sources could be recommended for cardiovascular disease prevention.